Need some help on this one... 1987 Merc 35 HP Outboard. Wont idle under 1500 - 1700 RPM. When I disconnect the fuel line, it will idle perfectly untill the carb bowl runs out of fuel. I bypassed my fuel system with a neighbors fuel tank...same problem. I put in a new needle and seat...same problem. Does the fuel pump have any high pressure shut off capabilities or is that the job of the needle and seat? Any suggestions?